The invention relates to an electrooptical scanning device for the detection of at least two oblong register marks extending at right angles to the direction of movement and arranged side by side or in series on webs moved in the longitudinal direction thereof with an optical scanning head located above the web having an illuminating device and at least two lenses, by means of which the two marks are represented on in each case one photodetector associated therewith, whereby conclusions can be drawn on the association of the register marks from the output signals of the photodetectors.
Electrooptical scanning devices of this type are used in the printing industry for so-called register adjustment which serves, particularly in the case of multicolor printing, to bring about a perfect alignment between the printing rollers and the webs of paper.
An electrooptical scanning device is already known, which permits the scanning of register marks which are both juxtaposed and in series, in that the scanning head containing two incorporated sensors can be rotated by 90.degree.. However, in this known solution, it is necessary to use further lamps with a filament twisted by 90.degree.. This requirement and the relatively complicated rotary mounting of the scanning head lead to a relatively costly scanning device, whereby account must also be taken of additional expenditure in time for changing over. The considerable expenditure for the rotary mounting of the scanning head is necessary in order to satisfy the high precision requirements on such a scanning head.